1. Field of the Invention
The present invention relates to a scroll compressor. More particularly, it relates to an improvement in a gas intaking means for introducing gas into a compression chamber.
2. Discussion of Background
The principle of a scroll compressor will be briefly described with reference to FIG. 7.
In FIG. 7, a reference numeral 1 designates a stationary scroll, a numeral 2 designates an orbiting scroll, a numeral 3 designates a compression chamber formed between the stationary and orbiting scrolls combined together and a numeral 4 designates a discharge port formed in the stationary scroll 1.
The stationary and orbiting scrolls 1, 2 respectively have a wrap having the same shape in cross section in a state that they are combined with each other in 180.degree. shifted condition. Each of the wraps has a shape constituted by an involute curve or the combination of arcs. The compression chamber 3 is formed by the combination of the wraps of the stationary and orbiting scrolls 1, 2. An intake port is formed at the outer periphery of the stationary scroll 1 to be communicated with the compression chamber 3.
In the operation of the scroll compressor, in which the orbiting scroll 2 is combined with the stationary scroll 1 which stands still in space, as shown in FIG. 7, the orbiting scroll 2 moves around the center of the stationary scroll 1 without movement of rotation, namely, a posture in angle of the orbiting scroll 2 is fixed. With the orbiting movement of the orbiting scroll 2 assuming successive movements as shown in FIGS. 7a, 7b, 7c and 7d, the volume of the compression chamber 3 gradually decreases with the result that the gas sucked in the compression chamber 3 is compressed as the chamber 3 moves to the central portion of the stationary scroll 1, and the compressed gas is finally discharged through the discharge port 4.
FIG. 8 is a cross-sectional view showing the construction of the conventional scroll compressor disclosed in, for instance, Japanese Unexamined Patent Publication No. 206989/1985. The disclosed scroll compressor is the typical low pressure shell type scroll compressor.
In FIG. 8, a reference numeral 1 designates a stationary scroll, a numeral 2 an orbiting scroll, a numeral 3 a compression chamber, a numeral 4 a discharge port, a numeral 5 a discharge tube communicated with the discharge port 4, a numeral 6 an orbiting scroll shaft formed on the orbiting scroll 2, a numeral 7 a crank shaft, a numeral 8 an eccentric opening formed in the crank shaft 7, the orbiting scroll shaft 6 being fitted in the eccentric opening, a numeral 9 an eccentric bush provided in a space between the inner wall of the eccentric opening 8 and the outer surface of the orbiting scroll shaft 6, which constitutes a variable radius crank mechanism, a numeral 10 the rotor of an electric motor, a numeral 11 the stator of the motor, numerals 12 and 13 respectively designate housings which serve as bearings, a numeral 14 designates a primary bearing interposed between the crank shaft 7 and the housing 12 to reduce friction resulted therebetween, a numeral 15 a secondary bearing for supporting the crank shaft 7, a numeral 16 a thrust bearing which is in contact with the lower surface of the orbiting scroll 2 to bear a pressure produced in the compression chamber 3 and the dead weight of the orbiting scroll 2, a numeral 17 an Oldham coupling in a ring form in which a pair of projections are respectively formed in the upper and lower surfaces at their edge portions in the lines crossing at the right angle. The Oldham coupling is to prevent movement of rotation of the orbiting scroll 2 but to causes the orbiting movement. A reference numeral 18 designates a tip seal fitted in a groove formed in the end surface of the wrap of each of the stationary and orbiting scrolls 1, 2, a numeral 19 a first balancer formed integrally with the crank shaft 7, a numeral 20 a second balancer attached to the lower part of the rotor 10 of the motor, a numeral 21 a shell, a numeral 22 an intake tube, a numeral 23 a forming-prevention plate and a numeral 24 an oil pump attached to the lower end of the crank shaft 7.
The operation of the scroll compressor having the construction as above-mentioned will be described. When a current is supplied to the stator 11 of the motor, a torque is produced in the rotor 10 and the rotor is rotated with the crank shaft 7. The rotation of the crank shaft transmits the torque to the orbiting scroll shaft 6 which is fitted in the eccentric bush 9 eccentrically provided on the crank shaft 7. The orbiting scroll 2 undergoes the orbiting movement by the Oldham coupling 17 to thereby perform a compressing function as shown in FIG. 7. In the compressing function of the scrolls, leakage of the compressed gas from a first compression chamber at a high pressure to a second compression chamber at a low pressure in the radial direction of the scrolls is prevented because the tip seals are fitted in the grooves in the end surfaces of the wraps and seal gaps which may be produced between the bottom surface of the scrolls and the end surfaces in the axial direction of the shell.
Leakage of the compressed gas in the circumferential direction is prevented by the mutual contact of the side surfaces of the wraps of the stationary and orbiting scrolls 1, 2. The mutual contact can be effected by providing eccentricity to the eccentric bush 9 and by utilizing a centrifugal force resulted by the orbiting movement of the orbiting scroll 2.
The gas to be supplied into the shell 21 through the intake tube 22 cools the rotor 10 and the stator 11 of the electric motor, and thereafter the gas is introduced into a compression chamber 3 through the intake port. The gas is compressed in the chamber 3, and then, is discharged out of the scroll compressor through the discharge tube 5.
The conventional scroll compressor is insufficient to provide a high volumetric efficiency which can be obtained by introducing a greater volume of the gas to be compressed when the gas is sucked in the compression chamber 3 through the intake port. Further, it is necessary to change major parts such as the scrolls in order to change the capacity of the scroll compressor.